Question 109529
Find N? 
I presume you mean Find n, because I don't see any N:
72(n+6)-80(n) = 200 Simplify the left side.
72n+432-80n = 200
-8n+432 = 200 Subtract 432 from both sides.
-8n = -232 Divide both sides by -8.
n = 29

{{{72n*n = 72n^2}}} Substitue n = 29
{{{72n^2 = 72(29)^2}}} = {{{72(841) = 60552}}}